Compensated antenna



March 19, 1963 N. SHYHALLA 3,082,421

- COMPENSATED ANTENNA Filed Jan. 26, 1960 NICHOLAS SHYHALLA m f w3,082,421 COMPENdATEB ANTENNA Nicholas Shyhalla, Niagara Falls, N.Y.,assignor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Filed .ian. 26, 196i Ser. No.4,821 4 {Zia-rims. {61. 343-114) The present invention relates toantennas and more particularly to antennas of such a configuration thatit will be decoupled from its mount.

When it is attempted to mount directional antennas on missiles or otherairframes, distortion of the antenna patterns is usually encountered.This results from the fact that the airframe itself may be a reasonablyeflicient antenna and the airframe, considered as an antenna, is coupledto the directional antenna. This tends to make the resulting antennapattern resemble that of the airframe rather than the intendeddirectional pattern. The result is that at very high frequencies (VHF)(30 to 300 megacycles) small direction-finding antennas becomeimpractical, especially for horizontally-polarized radiation, since inthis case the missile pattern becomes more serious.

An object of the present invention is the provision of an antennaconfiguration which will cancel the coupling between the antenna and itsmount.

Another object is to provide an antenna which will cancel the couplingbetween the antenna and its mount, thus making it possible to detectpolarized radiated signals.

Other objects and many of the attendant adantages of this invention willbe readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing wherein there is shown apreferred embodiment of the invention.

As shown, the antenna assembly comprises four closed loops 1! 11, 12,and 13 positioned symmetrically about an axis 14 in an airframe ormissile 20. Each of the four loops is connected across terminals 16 and18. Lead wires 19 are for connecting the antenna to a receiver, notshown.

The areas of loops and 11 and their radial distances from the missilelongitudinal axis are adjusted to give the same degree of coupling asbetween them and the missile frame 20 as exists between the pair ofloops 12 and 13 and the missile frame 20.

In use, the antenna could be mounted in a missile or airframe forreceiving VHF command radio signals. For a missile that is symmetricalabout the longitudinal axis, the antenna assembly is also symmetricalabout this axis. The VHF command radio signals to be received by theantenna are polarized in the horizontal plane and, in this plane, theradiation pattern obtained with the loop antenna described is a figureeight with nulls in alignment with the missile longitudinal axis. Theproperties of the loop antenna and the theory upon which theseproperties depend are set forth on pages 907-908 of Electronic and RadioEngineering, by Frederick Emmons Terman, 4th Edition, 1955,McGraw-l-Iill Book Company. Left-right horizontally polarized commandsignals are picked up only by horizontal loops 12 and 13, the verticalloops 1t) and 11 picking up essentially no radiation directly. Theoutput of loops 12 and 13 is a left-right error signal which 3,8Z,4ZlPatented Mar. 19, 1963 is zero for straight ahead and is proportional tothe difference in the time of arrival of the radiating signal at loopsl2 and 13. This error signal is fed to a control circuit, not shown, forcontrolling the flight of an aircraft or missile. All four loops 10, 11,12 and 13 are adjusted to give the same degree of coupling between themand the missile frame. The interconnection of the loops makes theseseparate couplings cancel each other.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. In combination with an airframe, a very high frequency receivingantenna assembly mounted in said airframe, said antenna assemblycomprising a plurality of closed loops mounted in a horizontal plane, aplurality of closed loops mounted in a vertical plane, the areas andpositions with respect to said airframe of said vertically andhorizontally mounted loops being adjusted to give the same degree ofcoupling between said loops and said airframe, and means connecting saidloops to make the couplings from said vertical loops cancel thecouplings from said horizontal loops.

2. In a very high frequency directional radio receiving antenna systemadapted to be mounted in an aircraft: the combination comprising a firstpair of closed loops mounted in a horizontal plane, a second pair ofclosed loops mounted in a vertical plane, said first and second pair ofloops being positioned relative to each other to give the same degree ofcoupling between them and the aircraft, said first and second pair ofloops being interconnected to thereby cause the couplings between saidmissile and said loops to cancel.

3. In a missile, a very high frequency directional radio receivingantenna mounted in said missile, said receiving antenna comprising afirst pair of closed loops symmetrically mounted in a horizontal planeabout the center line of said missile, a second pair of closed loopssymmetrically mounted in a vertical plane about the center line of saidmissile, said first and second pairs of loops being connected inparallel to effectively decouple said antenna from said missile.

4. In a missile, a very high frequency receiving antenna mounted withinthe airframe of said missile for receiving horizontally polarized radiosignals, said receiving antenna comprising first, second, third, andfourth closed loops, the areas of said loops and positions with respectto said airframe being such as to provide the same degree of couplingbetween said loops and said airframe, said first and third loops lyingin the horizontal plane, said second and fourth loops beingperpendicular to said first and third loops, first and second electricalconnector means to connect all of said loops in parallel such that thecouplings between said loops and said airframe are effectivelycancelled.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN COMBINATION WITH AN AIRFRAME, A VERY HIGH FREQUENCY RECEIVINGANTENNA ASSEMBLY MOUNTED IN SAID AIRFRAME, SAID ANTENNA ASSEMBLYCOMPRISING A PLURALITY OF CLOSED LOOPS MOUNTED IN A HORIZONTAL PLANE, APLURALITY OF CLOSED LOOPS MOUNTED IN A VERTICAL PLANE, THE AREAS ANDPOSITIONS WITH RESPECT TO SAID AIRFRAME OF SAID VERTICALLY ANDHORIZONTALLY MOUNTED LOOPS BEING ADJUSTED TO GIVE THE SAME DEGREE OFCOUPLING BETWEEN SAID LOOPS AND SAID AIRFRAME, AND MEANS CONNECTING SAIDLOOPS TO MAKE THE COUPLINGS FROM SAID VERTICAL LOOPS CANCEL THECOUPLINGS FROM SAID HORIZONTAL LOOPS.